Ambient fine particles (particulate matter less than 2.5 m aerodynamic diameter, or PM2.5) have been reported to be associated with a variety of health outcomes including mortality, morbidity, lung functions, and respiratory symptoms. In recent years, an increasing number of studies have shown associations between fine particles and an array of specific cardiovascular outcomes and functions including heart rate variability, blood pressure, and onset of acute myocardial infarction. The main objective of this proposed project is to examine the association between ambient fine particles and the out-of-hospital cardiac arrests in New York City, where residents are exposed to both traffic- related fine particles and regional sulfates that are transported from mid-west coal-fired power plants. We will utilize two sets of unique out-of-hospital cardiac arrest data: (1) the Pre-Hospital Evaluation of New York Cardiac Survival (PHENYCS) study data, that have been collected by the Fire Department of New York and Emergency Medical Service (FDNY/EMS), the New York Academy of Medicine (NYAM), and Long Island Jewish Medical Center (LIJMC) between April 2002 and March 2003;and, (2) SmartCPR Trial data, which are being collected by the FDNY/EMS for the study period May 2006 through April 2009. The database includes detailed information on the subjects at location of the arrest that will allow examination of effect modifiers. The cases (~4,600 in PHENYCS;~14,000 in SmartCPR) also include a large fraction of minority populations (31% African-American and 16% Latino). Specific aims are: (1) to determine the relationship between the short-term changes in the citywide average PM2.5 and the out-of-hospital cardiac arrests;(2) to determine the role of source type of PM2.5 (i.e., traffic vs. transported sulfate) that may be responsible for the association;and, (3) to determine effect modifiers and risk factors of PM2.5 effects in the large urban population. A case-crossover study design will be used to determine the relationships between PM2.5 concentrations and out-of-hospital cardiac arrests. Traffic-related air pollution exposure will be estimated to stratify the data. This proposed study is relevant in determining the public health risks of exposures to major sources of ambient fine particles. PUBLIC HEALTH RELEVANCE: The main objective of this proposed project is to examine the association between ambient fine particles and the out-of-hospital cardiac arrests in New York City, where residents are exposed to both traffic-related fine particles and regional sulfates that are transported from mid-west coal-fired power plants. This proposed study is relevant in determining the public health risks of exposures to major sources of ambient fine particles.